Mercedes and BMW had several years of severe quality control issues from, oh, late 90s to 2005-6. Not across every model, and not equally for both makes, but there's a lot of evidence of issues.
During that time, Honda and Toyota were making wonderfully reliable cars. But look at the recent toyotas.
Same story for American cars. The last few years Ford has been making cars w/ the fewest defects. But perception lags.
The good thing is, there are consumer reports and other agencies that track defects per 1000 cars. I've bought 2 Mercedes cars since 2007 and they both have ranked wonderfully on the consumer reports and, anecdotally, my ownership has been entirely free of defects.
I'm not sure what you mean about "4000 a year to maintain" a car that was brand new. Yes, I do have to have the oil changed yearly, and there are other maintenance tasks at normal intervals. But $4000 a year in maintenance on a Mercedes is fiction.
where the guy talks about spending $5K in one particular year, which appears to be the first year he had it.
likely an exaggeration on my part, mea culpa, but the reviews on that site are full of maintenance complaints:
it's entirely anecdotal but I had a friend who had two BMWs and both were constantly in and out of the shop. this was a long time ago, though. ymmv (literally).